There are numerous applications, for example, in turbine split casings for power generation, wherein a very high torque must be applied to a stud to rotate the same. No effective wrench is known for wrenching such studs. Accordingly, torches and similar awkward means must presently be used to remove the studs. This is a very time-consuming, expensive, and destructive operation.
High torque ratchet wrenches and related prior art are described in U.S. Pat. Nos. 4,091,890 and 4,132,136, assigned to the same assignee. Such ratchet wrenches for loosening or tightening nuts and bolts do not lend themselves for wrenching applications such as described above, because the required high torques would produce substantial bending and tensile forces in the housing of the ratchet wrench, requiring such housing to be made very large and heavy to maintain its structural integrity. Also, conventional ratchet wrenches would not develop a sufficient prior clamping force on the stud to be wrenched, so that the required torque could not be effectively transmitted to and maintained on the stud.
Drill pipe tongs are also well known and are used in making up or breaking apart drill pipe joints. Typical such tongs are described in U.S. Pat. Nos. 4,082,017 and 3,844,547. Such tongs include hydraulically or pneumatically powered upper and lower tongs which are swivelly connected for a scissoring action. Each of the tongs typically includes a door that is hingedly mounted at one edge and is provided with a latch at the other edge to enable the door to be swung to a completely open position for removal of the tongs from the drill pipe when desired.